Laser diodes comprising QWI output window and waveguide areas and methods of manufacture

Abstract

In accordance with one embodiment of the present disclosure, a process of manufacturing a semiconductor laser diode comprising a gain section, a QWI output window, and QWI waveguide areas is provided. The QWI waveguide areas are fabricated using quantum well intermixing and define a QWI waveguide portion in the QWI output window of the laser diode. The QWI output window is transparent to the lasing wavelength λL. The QWI waveguide portion in the QWI output window is characterized by an energy bandgap that is larger than an energy bandgap of the gain section such that the band gap wavelength λQWI in the QWI waveguide portion and the QWI output window is shorter than the lasing wavelength λL. The QWI output window is characterized by a photoluminescent wavelength λPL. The manufacturing process comprises a λPL screening protocol that determines laser diode reliability based on a comparison of the lasing wavelength λL and the photoluminescent wavelength λPL of the QWI output window. Additional embodiments are disclosed and claimed.

1. A process of manufacturing a semiconductor laser diode comprising a gain section, a QWI output window, and QWI waveguide areas, wherein:
 the semiconductor laser diode is characterized by a lasing wavelength λ L ; 
 the QWI waveguide areas are fabricated using quantum well intermixing and define a QWI waveguide portion in the QWI output window of the laser diode; 
 the QWI output window is transparent to the lasing wavelength λ L ; 
 the QWI waveguide portion in the QWI output window is characterized by an energy bandgap that is larger than an energy bandgap of the gain section such that the band gap wavelength λ QWI  in the QWI waveguide portion and the QWI output window is shorter than the lasing wavelength λ L ; 
 the QWI output window is characterized by a photoluminescent wavelength λ PL ; and 
 the manufacturing process comprises a λ PL  screening protocol that determines laser diode reliability based on a comparison of the lasing wavelength λ L  and the photoluminescent wavelength λ PL  of the QWI output window. 
 
     
     
       2. A process as claimed in  claim 1  wherein the energy bandgap of the QWI output window is determined by measuring the photoluminescent wavelength λ PL  of the QWI areas including the QWI output window. 
     
     
       3. A process as claimed in  claim 2  wherein the photoluminescent wavelength λ PL  of the QWI output window is determined after the QWI waveguide areas are fabricated using quantum well intermixing. 
     
     
       4. A process as claimed in  claim 2  wherein the photoluminescent wavelength λ PL  of the QWI output window is determined by measuring luminescence spectra. 
     
     
       5. A process as claimed in  claim 1  wherein:
 the semiconductor laser diode further comprises one or more passive sections; 
 the QWI waveguide areas further define a QWI waveguide portion in the passive sections of the laser diode; 
 the QWI waveguide portion in the passive sections of the laser diode is characterized by an energy bandgap that is larger than an energy bandgap of the gain section; 
 the photoluminescent wavelength λ PL  of the QWI output window is determined by referring to a determination of photo-current I PHOTO  resulting from optical absorption at one or more of the passive sections of the laser when the gain section is electrically pumped to produce lasing light. 
 
     
     
       6. A process as claimed in  claim 5  wherein the photo-current I PHOTO  resulting from optical absorption at one or more of the passive sections of the laser is determined according to the following relation:
     I   PHOTO   =I   PHASE −( V   GAIN   −V   PHASE )/ R  
 
 
       where I phase  is the total current at the passive section, V GAIN  is the voltage drop on the gain section, V PHASE  is the voltage drop on the passive section, and R represents an isolation resistance between the passive section and the gain section. 
     
     
       7. A process as claimed in  claim 6  wherein the passive section comprises a phase section of a three section DBR laser. 
     
     
       8. A process as claimed in  claim 6  wherein the λ PL  screening protocol determines that the laser diode is reliable when the photo-current I PHOTO  is less than 2 mA depending on the heat-sink temperature and the gain-section current. 
     
     
       9. A process as claimed in  claim 1  wherein:
 the semiconductor laser comprises a three section DBR laser comprising one or more passive sections; 
 the passive sections of the DBR laser comprise a wavelength selective DBR section and a phase section; and 
 the photoluminescent wavelength λ PL  of the QWI output window is determined by referring to a determination of photo-current I PHOTO  resulting from optical absorption at the phase or DBR section of the laser when the gain section is electrically pumped to produce lasing light. 
 
     
     
       10. A process as claimed in  claim 1  wherein:
 the semiconductor laser is characterized by a critical absorption wavelength λ C ; and 
 the λ PL  screening protocol determines laser diode reliability by determining whether the photoluminescent wavelength λ PL  of the QWI output window is low enough to ensure that the corresponding temperature at which λ C =λ L  falls outside of the operating temperature range of the laser. 
 
     
     
       11. A process as claimed in  claim 1  wherein the lasing wavelength λ L  is approximately 1060 nm and the λ PL  screening protocol determines laser diode reliability by determining whether the photoluminescent wavelength λ PL  of the QWI output window is less than approximately 99 nm. 
     
     
       12. A process as claimed in  claim 1  wherein the lasing wavelength λ L  is approximately 1060 nm and the λ PL  screening protocol determines laser diode reliability by determining whether the energy band gap of the QWI output window is at least 79 meV larger than that corresponding to the lasing wavelength λ L . 
     
     
       13. A process as claimed in  claim 1  wherein the semiconductor laser diode comprises a DBR laser diode and the passive sections of the laser diode comprise a wavelength selective section, a phase section, or both. 
     
     
       14. A process as claimed in  claim 1  wherein the QWI output window of the semiconductor laser diode is cleaved in air. 
     
     
       15. A process of manufacturing a semiconductor laser diode comprising a gain section, a QWI output window, and QWI waveguide areas, wherein:
 the semiconductor laser diode is characterized by a critical absorption wavelength λ C  and a lasing wavelength λ L ; 
 the QWI waveguide areas are fabricated using quantum well intermixing and define a QWI waveguide portion in a QWI output window of the laser diode; 
 the QWI output window is transparent to the lasing wavelength λ L ; 
 the QWI waveguide portion in the QWI output window is characterized by an energy bandgap that is larger than an energy bandgap of the gain section such that the band gap wavelength λ QWI  in the QWI waveguide portion and the QWI output window is shorter than the lasing wavelength λ L ; 
 the QWI output window is characterized by a photoluminescent wavelength λ PL ; and 
 the manufacturing process comprises a λ PL  screening protocol that determines laser diode reliability by determining whether the photoluminescent wavelength λ PL  of the QWI output window is low enough to ensure that the corresponding temperature at which λ C =λ L  falls outside of the operating temperature range of the laser.